Abstract
Nutrient uptake is strongly influenced by plant growth rate. Accelerated growth leads to nutrient levels incapable of sustaining the optimal growth rate, resulting in shoot to root signaling for increased nutrient absorption. The factors controlling nutrient demand in turfgrass and its consequences have not been investigated. The objectives of this research were to verify that turfgrass exhibits the principal characteristics of demand-driven nutrient uptake and to identify the primary factor controlling nutrient demand via regulation of growth rates. Kentucky bluegrass clipping production increased linearly up to annual fertilizer N rates of 600 kg ha−1 and to 1000 kg N ha−1 for creeping bentgrass. At the typical annual N fertilization rates of 150 to 300 kg ha−1 for the two grasses, N supply was the primary determinant of turfgrass growth rate, plant nutrient demand, and nutrient uptake. Nitrogen uptake accounted for over 88% of uptake of all other nutrients. Uptake of P and K were strongly related to tissue N content irrespective of soil test levels. Variations in turfgrass species and cultivar nutrient requirements and nutrient use efficiencies were found to be directly related to differences in growth rates and, by inference, to differences in nutrient demand.
Highlights
Nutrient demand is well established as having strong control over plant responses to varying external nutrient supplies [1,2,3,4]
If plant growth rate regulates nutrient demand and is the principal driving force for nutrient uptake [1,2,3,4], nutrient uptake should be strongly dependent on growth rate
This was evident in data from Experiment 1, where regressions of nutrient uptake on creeping bentgrass growth rates yielded R2 values ranging from 0.910 to 0.982 for N, P, and K (Figure 1) and 0.884 to 0.932 for Ca, Mg and S (Figure 2)
Summary
Nutrient demand is well established as having strong control over plant responses to varying external nutrient supplies [1,2,3,4]. Cooper and Clarkson [13] and Marschner et al [14] have confirmed the rapid xylem-phloem cycling and recycling of nutrient ions and certain metabolites in plants, thereby lending credence to White’s [12] hypothesis. This rapid cycling and recycling of nutrient ions and metabolites has become accepted as the basic means whereby shoot to root signaling of whole plant nutrient status is achieved and leads to integration of root membrane nutrient absorption rates with whole plant nutrient demand [13]
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